This invention relates to an apparatus for measuring the coefficient of friction of a golf ball.
As is known, the coefficient of friction of a golf ball has a direct effect on the amount of spin imparted to a golf ball when hit by a golf club. That is to say, the measurement of friction between the golf club and the golf ball is important in assessing the spin characteristics of a golf ball, particularly for a high lofted iron. Traditionally, it has been accepted that the back spin imparted to a golf ball is that which enables a player to stop the ball on a green. However, the main function of a back spin is not to stop the ball on a green but to provide aerodynamic lift that prolongs flight time.
As described by Gobush W., "Spin And The Inner Workings Of A Golf Ball", Golf The Scientific Way edited by A. J. Cochran, Aston Publishing Group, 1995, pages 141-145, there are two components of force which act on a golf ball during impact with an iron. One force is at a right angle to the club face and is represented as the vector F.sub.N and the other force is parallel to the club face or tangential to the golf ball and is designated as the vector F.sub.T. The normal force F.sub.N projects the ball forward while the tangential force F.sub.T applies spin. The ratio of these two forces represents the coefficient of friction of the ball on the club face.
In the past, various types of techniques have been used to obtain a measurement of the coefficient of friction of a golf club face. One technique employs an air cannon which is used to eject golf balls at a force transducer surface and a camera system which is used to capture the golf ball at positions before and after impact with the force transducer. However, such a technique requires relatively cumbersome types of structures and requires photographic analysis of the golf ball.